This invention relates to a method for the catalytic oxidation of alcohols, and in particular, to a method for the selective oxidation of alcohols catalyzed by manganese oxides.
The oxidation of alcohols to carbonyl compounds is of great interest to academia and industry, particularly the fine chemicals industry. A number of catalytic oxidations of alcohols in which oxygen is the secondary oxidant have been reported, using ruthenium, cobalt, copper, palladium, and platinum metal catalysts with additives such as potassium carbonate, sodium bicarbonate, pyridine, molecular sieves, and phenanthroline.
Stoichiometric metal oxidants such as chromium (VI) compounds and active manganese dioxide have also been widely used, particularly for the oxidation of allylic and benzylic oxidations. The reactivity of active manganese oxide is inconsistent, depending on preparation methods, compositions, and structure. Complicated preparation methods are often necessary, and the use of freshly made active manganese oxide is required. Moreover, five to fifty equivalents of these reagents are required to obtain oxidation products, resulting in large amounts of non-reusable, toxic waste. Use of peroxides gives rise to handling hazards.
There accordingly remains a continuing need for cost-effective, efficient, and environmentally friendly methods for the selective oxidation of primary and secondary alcohols to their corresponding aldehydes and ketones.
A method of oxidizing alcohols comprises reacting an alcohol with oxygen in the presence of an effective amount of a manganese-containing octahedral molecular sieve or a manganese-containing octahedral layer material.
A preferred manganese-containing octahedral molecular sieve has the formula
A2xe2x88x92yMn8O16.xH2O
wherein A is H+, Na+, or K+, y is about 0.5 to about 1.5, and x is 0 to about 20.
Another preferred manganese-containing octahedral molecular sieve has the formula
A2xe2x88x92yMnO2xe2x88x92z(PO4)z.xH2O
wherein A is H+, Na+, or K+, y is preferably about 0.5 to about 1.5, z is greater than zero to two, and x is 0 to about 20.
Still another preferred manganese octahedral material is a co-synthesized mixture of gamma-manganese oxide and one of the above-described manganese-containing octahedral molecular sieves.